The present invention relates to heat treatment apparatus used in heating processing and the like for semiconductor wafers and other objects to be treated.
FIG. 6 shows one portion of a generally used type of heat treatment apparatus used in the manufacture of semiconductors, for CVD processing and for oxidation by heat treatment of semiconductors. This heat treatment apparatus is provided with a process tube 4 which is the processing chamber which implements a required processing such as heating or the like to wafers 2 which are the object to be processed. To the lower side of this process tube 4 is provided a load lock chamber 8 via a manifold 6 which is configured from stainless steel or the like. The manifold 6 is a cavity portion for connecting the process tube 4 and the load lock chamber 8, and the load lock chamber 8 is a blocking chamber for blocking the outside air from the wafers 2 either prior to or after treatment thereof by the process tube 4.
The process tube 4 is formed of a heat-resistant material such as silica glass or the like which does not exert an influence with respect to the objects being processed, and is a cylindrical shape with one end closed, and is disposed immediately above the upper portion of the load lock chamber 8. In this manner, the treating furnace with the process tube 4 immediately above it is called a vertical type furnace. Around this process tube 4 is a heater 10 for performing heating or some other necessary process with respect to the wafers 2. This heater 10 performs electrical heating control and so is connected to a heating control apparatus. The treatment temperature of the process tube 4 is set to 500.degree.-1000.degree. C. for the CVD process, or to 800.degree.-1000.degree. C. for oxidation treatment or diffusion treatment.
To the manifold 6 which is disposed to the side of the lower end of this process tube 4 is provided a gas introduction tube 12 for the introduction of a treatment gas G.sub.1 corresponding to the treatment, into the process tube 4, and this gas introduction tube 12 is connected via a control valve or the like to a gas source (not shown). For example, SiH4 is used as the treatment gas for CVD treatment when a polysilicon film is to be formed, and NH.sub.4, SiH.sub.2 Cl.sub.2 is used as the treatment gas when a silicon nitride film is to be formed, and these gases are introduced into the process tube 4 via the gas introduction tube 12, and N.sub.2 gas or the like is introduced into the process tube 4 as the purge gas.
The inside of this process tube 4 is provided with a cylindrical partition wall formed of a heat resistant material such as silica glass or the like. After the treatment gas which has been introduced from the gas introduction tube 12 moves from the side of the manifold 6 and from the bottom to the top of the process tube 4, it moves to the outer side of the partition wall 14 and again returns to the manifold 6. More specifically, the manifold 6 of the outer surface portion of the partition wall 14 is connected to an exhaust pipe 16 which is the exhaust portion for the exhaust of the air in the initial status, or the treatment gas G.sub.1 which has been recirculated, and this exhaust pipe 16 is connected to a vacuum apparatus such as a vacuum pump or the like (not shown). The air and the treatment gas G.sub.1 which has been introduced are forcedly exhausted from the process tube 4 through the vacuum apparatus.
In addition, the wafers 2 which are the object of treatment are carried into the process tube 4 by a wafer boat 18 from the load lock chamber 8 via the conveyor chamber 8a. In addition, to the opening portion 19 on the side of the load lock chamber 8 of the manifold 6 is provided a shutter 20 as an interrupt means between the load lock chamber 8 and the process tube 4. This shutter 20 swivels along with unloading and closes the opening portion 19 of the manifold 6 when there wafer boat 18 is unloaded from the process tube 4.
Furthermore, the load lock chamber 8 is provided with a boat elevator 22 as the raising and lowering mechanism for raising and lowering the wafer boat 18 and for loading and unloading the wafers 2 to and from the process tube 4. To the upper surface of this boat elevator 22 is provided a heat retention cylinder 24 for supporting the wafer boat 18 and forming a region of uniform temperature. When the wafer boat 18 is unloaded, this heat retention cylinder 24 seals the open surface of the manifold 6 and so forms a cap 26, while the arm portion 22a of the boat elevator 22 has a flat plate 26a comprised of stainless steel, and between this flat plate 26a and the cap 26 is a coil spring 26b arranged at three places for example. More specifically, when the objects for treatment are being loaded into the process tube 4, the shutter 20 swivels and opens, the boat elevator 22 rises, and the manifold 6 is sealed by the cap 26 of the heat retention cylinder 24 and the process tube 4 is blocked off from the load lock chamber 8.
In addition, the wall surface portion of this load lock chamber 8 is provided with a gate 28 through which is performed the carrying in of the wafers 2 from the conveyor chamber 8a prior to treatment and the carrying out of the wafers 2 from the load lock chamber 8 after treatment, and this gate 28 is provided with a gate valve for blocking the load lock chamber 8 and the conveyor chamber 8a. The wall surface portion of the load lock chamber 8 is provided with a gas introduction pipe 30 and an exhaust pipe 32, and the gas introduction pipe 30 is connected to a gas source for an inert gas which is the purge gas G.sub.2 or the like. More specifically, the purge gas G.sub.2 is supplied from the gas introduction pipe 30 to inside the load lock chamber 8, and a vacuum is made inside the load lock chamber 8 via the exhaust pipe 32, and either the creation of a vacuum or the exhaust of the supplied gas G.sub.2 are performed via the gas introduction pipe 30.
In such a conventional heat treatment apparatus, the boat elevator 22 is provided as the means for opening and closing the opening portion 19 of the manifold 6, and for the carrying in and out of the process tube 4, of the wafers 2 which are the object of treatment. Then, this boat elevator 22 is provided with a drive mechanism 34 which is configured by a ball screw or the like, for performing up and down motion. This boat elevator 22 has the wafer boat 18 and several tens of wafers 2 placed on it, and is supported by the cap 26 which seals the opening portion 19 of the manifold 6 but when the opening portion 19 of the manifold 6 is sealed, it is necessary for this cap 26 to be in gentle contact with the opening portion 19 of the manifold 6. There are cases when the manifold 6 is formed of stainless steel but when it is formed of silica glass or the like, there is the danger of it breaking should an impact be applied to the side of the manifold when the opening portion 19 is sealed. Furthermore, when there is such an impact force, the wafers 2 on the wafer boat 18 are moved and this generates particles which adhere to the wafers 2 and cause an adverse influence with respect to the film formation treatment. In addition, from the necessity of maintaining airtightness on the side of the manifold 6, it is necessary that the cap 26 and the opening portion 19 of the manifold 6 be sealed with a constant degree of adhesion.
In addition, even if the degree of verticality of the process tube 4 and the manifold 6 is set with a high precision, it is difficult to establish a degree of verticality for the wafer boat 18 which is mounted on the heat retention cylinder 24, and a degree of horizontality for the wafer boat 18. Furthermore, in the status where both the horizontality of the cap 26 and the verticality of the wafer boat 18 are not both established, closing the cap 26 to the manifold 6 means that the wafer boat 18 will be housed in the process tube 4 in an inclined status when the cap 26 is closed to the manifold 6. If film formation treatment is implemented to the wafers 2 when there is a status such as this, then there will be an eccentric recirculation density of the treatment gas with respect to the wafers 2 of the wafer boat 18 and there will be a loss of thermal uniformity because of the changes in the distance to the heater 10. This will result in non-uniform treatment with respect to the wafers 2, and there will be a higher incidence of faults.
Not only this, as shown in FIG. 7, a conventional horizontal type furnace has a lower end base portion of a diagonally moving member 170 pivoted by a horizontal shaft 180 to the moving unit 120 and this diagonally moving member 170 is provided horizontal to a cylindrical unit 190 which has one closed end. Moreover, a base portion of a cantilever 800 is supported to the inner surface of this cylindrical unit 190 by support members 200a, 200b and by a spring 210. Then, the outer periphery of the cylindrical unit 190 engages with a furnace opening door 700, and is supported by a spring 220, and a bellows 140 links the diagonally moving member 170 and the furnace opening door 700. A spring 130 which presses the door 700 to the furnace opening is inserted between the diagonally moving member 170 and the furnace opening door 700 (for example, see Utility Model Publication No. 24926-1989).
However, this type can only be applied to horizontal type furnaces and cannot be applied to vertical furnaces, and in addition, there is no heat retention for the wafer boat, there are no rotating portions, and there is also no implementation of heat insulation.